Plugin development: how to create a form and get custom data?

Question

I am developing a booking plugin and I need help.

My aim is to get data to and from a database from the WordPress admin menu (I created a custom menu page for it). Now I don't know how the form should be submitted to a PHP script in WordPress environment.

<!-- HTML FORM -->
<form method="post" action="<?php echo $_SERVER['REQUEST_URI']; ?>">
    <input type="text" name="reservation_capacity" placeholder="Reservation Capacity" />
    <input type="button" name="Add Table" value="Add New Table" />
</form>

I would also need help as to how the plugin would create a form on the website and get data from their as well!

Answer 1

The details of processing form data is specific to PHP therefore I will not go into it. The WordPress-specific part is that you want your code to be run on the 'init' event in order to have access to WordPress functions and globals (such as the users permissions).

<?php add_action('init', function(){
    $reservation_capacity = sanitize_text_field( $_POST['reservation_capacity'] );
    update_user_meta( get_current_user_id(), 'reservation_capacity', $reservation_capacity );
}); ?>

This is just an example where you save the form value to the users meta database (that you probably wouldn't use in real life). sanitize_text_field is one of many WP specific functions to sanitize input values. get_current_user_id becomes available after init if a user is logged-in.

More on the topic:

• Validating Sanitizing and Escaping User Data
• Data Validation
• Validating, Sanitizing, and Escaping
• Data Sanitization and Validation With WordPress